On Thursday, February 14, 2002, at 08:12 PM, Michael Fowler wrote:
> On Thu, Feb 14, 2002 at 04:14:39PM -0500, Ian P. Thomas wrote:
>>
>> # The array, unchecked_dfa_states, is going to be an array of arrays
>> ( 2-D ).
>> # dfa_state_creation is a subroutine that returns an array, and takes
>> an array
>> # or single number, and a scalar, as parameters.
>
>> push @unchecked_dfa_states, [ dfa_state_creation( $nfa_start_state,
>> $epsilon ) ];
>> # I want it to loop until this array is empty.
>> while ( $#unchecked_dfa_states > 0 )
>
> The typical idiom is:
>
> while (@unchecked_dfa_states)
>
>> {
>> # I remove the first array and add it to another 2-D array. Syntax
>> may be wrong.
>> @checked_dfa_state = shift( [ $unchecked_dfa_state[ 0 ] );
>
> shift expects an array, not an array reference. This won't even parse
> correctly, for that reason and because you have an unmatched bracket.
> Did
> you copy and paste your code, or type it in?
>
> What I believe you want is:
>
> @checked_dfa_states = @{ shift(@unchecked_dfa_states) };
>
> That pulls off the first element of @unchecked_dfa_states and
> dereferences
> it.
>
>
>> # alphabet is an array of symbols( letters or numbers )
>> foreach $symbol ( @alphabet )
>> {
>> # I'm having trouble here passing the array, as a whole, to the
>> subroutine. I don't # think that I'm getting the syntax right.
>> The subroutine will eventually return an array that will be
>> # pushed on to the 2-D array unchecked_dfa_states.
>> push(@unchecked_dfa_states, dfa_state_creation(
>> [ unchecked_dfa_states[ 0 ] ], $symbol ) );
>> } # End foreach.
>
> I believe you want:
>
> push(
> @unchecked_dfa_states,
> dfa_state_creation($unchecked_dfa_states[0],
> $symbol)
> );
>
> It's very hard to determine what it is you're trying to accomplish from
> your
> code and description. I'm not sure what's a typo and what's
> misunderstanding. If the above doesn't help you should send another
> message
> to the list describing more of what you want to happen, with at least
> parseable code.
>
>
> Michael
> --
> Administrator www.shoebox.net
> Programmer, System Administrator www.gallanttech.com
> --
>
I typed some of it in so there may have been some typos.
What I believe you want is:
@checked_dfa_states = @{ shift(@unchecked_dfa_states) };
If I read this correctly, I takes the first array from
unchecked_dfa_states and passes it out, but not before dereferencing
it. I needed something that could take the first array as a whole
object and pass it to checked_dfa_states, another array of arrays.
After pouring through my Perl books, I think what I needed to do was to
give each stored array in unchecked_dfa_states a scalar reference. This
way I could pass the reference to the whole array. Does that sound
right?
The alternative that I used was keeping two arrays. One just held
information about the size of the arrays in unchecked_dfa_states. I
called it unchecked_dfa_states_sizes. I did a for loop using a value
from the unchecked_dfa_states_sizes array as the ceiling to put each
element into a temporary array. I then pushed this temporary array onto
checked_dfa_states. The reason I was able to do this is because I kept
the two arrays,
unchecked_dfa_states
unchecked_dfa_states_sizes
in sync. That meant that every subscript for unchecked_dfa_states_sizes
matched a corresponding subscript for an array in unchecked_dfa_states.
A reference to an array, and a separate reference to its size. The
other part...
I believe you want:
push(
@unchecked_dfa_states,
dfa_state_creation($unchecked_dfa_states[0], $symbol)
);
I can't remember exactly, but I believe when I tried to do it this
way, it passed an actual numeric value, the memory address to the array
referenced by $unchecked_dfa_states[0]. As above, I stored the array
referenced by $unchecked_dfa_states[0] into a temporary array and passed
that in like this
dfa_state_creation( @temp, $symbol)
This worked. Thanks for the help. I think I need to spend some
more time with the animal books and reading this list. I ended up
having some problems using global variables later in the program. Next
time I'll cut and paste the code. :)
Ian P. Thomas
Of course it runs NetBSD
www.netbsd.org
